Fe3O4 nanoparticles-loaded PEG–PLA polymeric vesicles as labels for ultrasensitive immunosensors

A class of immuno-labels based on poly(ethylene glycol)–poly(lactic acid) (PEG–PLA) polymeric vesicles was developed in this study. To fabricate these immune-labels, the uniform Fe3O4 nanoparticles (NPs) were loaded into the vesicles followed by conjugating secondary antibody (Ab2) onto the vesicles surface, named Ab2–PEG–PLA–Fe3O4. The resulting Ab2–PEG–PLA–Fe3O4 demonstrated high catalytic activity towards H2O2, and the sensitivity of the sandwich-type immunosensor using this label for prostate specific antigen (PSA) detection increased greatly. The immunosensor based on this label exhibited high sensitivity, wide linear range (0.005–10 ng/mL), low detection limit (2 pg/mL), good reproducibility, selectivity and stability. These labels for immunosensors may provide many potential applications for the ultrasensitive detection of different cancer biomarkers. In addition, this technique also has the potential to be extended to the loading of other interesting material for preparing various kinds of labels to meet the different requirements in immunoassays.